I have a 522 pistol. Don’t really feel like going to the $450 expense to SBR it and put a Swiss folder on it.
But would kind of like to do a brace.
I have one of those rail adapter pieces that goes on the back end.
Just curious if anyone was using a brace or which would be the best?

SBtactical made the “compliant” pistol brace. The SBM4 brace fits tight and comfortable if shouldered.
Lanbo has the best price hands down.

Depends on which adapter you have. If its the M4 style, I put an SB Tactical brace tube and brace and its similar looking to the Swiss folder. The SB tube is a bit long however...longer than the Swiss stock with the SB brace on it. I lopped about 3/4" off (its solid aluminum at the rear) to keep total LOP below the 13.5" BATFE says is fine for a brace.

Here's a comparison against my SBR'ed 553 (before looping some length off)

I don’t have the adapter that the buffer tube screws into but the one that has the rail.

http://www.sigsauerguns.com/si...er-psb-1913-blk.html

I have not found any pictures of braces outside of what you posted but did find a picture with an MPX stock attached.
https://sigforum.com/eve/forums...0038044?r=3060038044

I think that looks pretty slick.
SB tactical essentially makes that in a brace so I do not see why it would not work.

https://www.sb-tactical.com/product/mpx-psb/

Not a brace but a stock....but I put the same adapter on my WCA 551 using a spare 556 lower, just to try it out.

the issue with the sliding version will be clearing all the controls. You won't know until you try.

No controls are blocked in the photos in the link above.

I’d love to just put a Swiss folder on it but a $250+ stock if you can find one and $200 tax stamp is hard to swallow for a gun I picked up for under $200.
$165 for the SB brace is much better of the price.